Cats open their mouths after sniffing something as part of a facial behavior called the Flehmen response. This reflex helps them analyze chemical signals—especially pheromones—by drawing scent molecules toward the vomeronasal organ (also known as Jacobson’s organ) located on the roof of the mouth. By curling the lips, lifting the nose, and slightly parting the mouth, they channel scents into this organ, which sends information directly to the brain about social cues, reproduction, territory, and other environmental details. Key points
- Purpose: enhanced detection of pheromones and other chemical cues beyond the main olfactory sense.
- Mechanism: openings at the roof of the mouth allow odor-laden air to reach the vomeronasal organ; the action is usually voluntary and often triggered by strong or unfamiliar scents (urine marks, new objects, sweat, etc.).
- Appearance: the mouth may look open in a characteristic grimace or “stinky face,” sometimes followed by a quick tongue movement.
When to be concerned
- Flehmen is normal in healthy cats and is typically short-lived. If a cat shows persistent facial grimacing, drooling, or other signs such as nasal discharge, facial swelling, or reluctance to swallow, a veterinary check is warranted to rule out dental or respiratory issues, infections, or blockages.
If you’d like, I can tailor this explanation to a specific context (e.g., cat behavior during a vet visit, multi-cat households, or differences across breeds).
